Submitted to: Environmental Pollution

2 Understanding the sources, distribution, storage and fate of metallic elements in arid river systems affected by mining is important in modeling their impacts on water and ecosystems. This paper reports on the distribution of Cd, Cu, Pb, Zn, Fe and Mn in aquatic systems draining the Mt Isa Ag-Cu-Pb-Zn Mine in arid northern Queensland, Australia. Analysis of fluvial sediment from the Leichhardt River, its tributaries draining the mine and associated near channel floodplain and cut riverbank environments indicates that both historic and contemporary contamination is continuing to impact the river system. Fine-grained, <180 um sediment stored within near channel overbank environments is the most contaminated, and in most cases is significantly in excess of background concentrations and Australian government sediment quality guidelines. Predicted changes in climatic conditions pose two main risks for arid areas such as the Leichhardt: increased evaporation may enhance aeolian transport of metals, while more intense storm events may result in the erosion and release of alluvial metals to floodplain environments and water resources downstream